1. Department of Physiology and Pharmacology, Karolinska Institute, 171 77 Stockholm, Sweden
2. Department of Radiology, Imperial College Hospital NHS Trust, London W12 0HS, UK
3. Department of Diagnostic Imaging, Monash Health, Melbourne 3168, Australia
4. Department of Cardiology, Royal Melbourne Hospital, Melbourne 3052, Australia
5. Department of Pulmonary Medicine, University of California, San Diego, CA 92037, USA
6. Department of Emergency Medicine, University of California, San Diego, CA 92103, USA